Process for the production of combinations of rubber and paper and products obtained thereby



Patented Dec. 29, 1925.

UNITED STATES PATENT- "OFFICE.

ERNEST HOP KINSON, OF NEW YORK, AND REED P. BOSE, OF JACKSON HEIGHTS, NEW YORK, .ASSIGNORS T0 GENERAL RUBBER COMPANY, OF NEW YORK, N. Y., A. COR

PORATION OF NEW JERSEY.

PROCESS FOR THE rnonucrron or oomnma'rxons or RUBBER AND PAPER AND rnonucrs OBTAINED THEBEBY.

No Drawing.

. To all whom it may concern: Y

Be it known that we, ERNEST HOIKINSON and REED P. Rosa, both citizens of the United States, and residents of New York, county and State of New York, and Jackson Heights, L. 1., county of Queens, State of New York, respectively, have invented certain new and useful Improvements in Processes for the Production of Combinations of Rubber and Paper and Products Obtained Thereby, of which the following; is a full.

clear, and exact description.

This invention relates to processes for the production of combinations of rubber and paper, particularly such combinations where the rubber in the form of a latex is combined with pulp of various kinds; and to the proclucts obtained thereby, which may be in the form of a continuous sheet or individual sheets. a;

The principal object of the present invention is to provide a simple eflicient process, which may be carried out entirely on the usual paper mill machinery, for the production of such combinations in which there, shall be a substantially homogeneous distribution of the rubber particles throughout the paper mass. Another object of the invention is to provide such a process in which collection of masses of rubber on the rolls and other parts of the machinery shall be in large part done away with. Another objcct of the invention is to provide a series of rubber-paper products of substantially homogeneous structure and having desirable physical characteristics such as high bursting and tensile strength, and in the case of comparativelythin sheet material, resistance to flexing.

This application is a continuation in part of our application Serial No. 700,425, filed March 19, 199/1. The invention accordingly includes a process for the manufacture of rubber and paper and similar combinations which comprises combining with pulp, which may be paper, asbestos or similar stock, a quantity of a rubber latex, agglomcrating the rubber particles in the mass, thencoagulating the same, and vulcanizing if desired. It also comprises rubber-paper Application filed October 22, 1925. Serial No. 64,242.

combinations vulcanized or not as desired havlng a range of rubber content up to 200% based on the weight of paper pulp.

The following is an exampleof a method of carrying out the process in connection with paper pulp: A batch of 1000 lbs. of kraft paper pulp is beaten with. about 15 to 20 times its weight of water. During the beating and preferably when it is about half finished a water solution of ammonia is added to the beater .in a quantity so that approximately 1-3 pounds of NH, per 100 lbs. of pulp is present. Beating is continued after the addition of this ammonia so that the fibres will be substantially completely impregnated with the ammoniacal solution. When the pulp has been beaten until it is 1n the condition ordinarily reached before passing on to the paper machine, or as the paper maker says when it has reached the desired slowness which is'a term "designating the hydration of the pulp,.rubber latex, preserved with 0.5%-3% NH based on the weight of the latex, diluted with an equal volume. of .water, to giver-the;.desired rubber content in the finished sheet is added. Beating is continued to distribute the latex throughout the pulp and to complete the preparation of the material for passage to the paper machine, For a beater containing 300 lbs. of the mass, beating up to the time of addition of the latex is ordinarily carried on for 2 hrs. After addition of the latex beating for approximately 1 hr. is continued. At the time that the ammonia is added to the pulp above, a vulcanizing compound may also be added. In practice We have found that 3 parts of precipitated sulphur, 1 part of zinc dimethyldi'thiocarbamate and 0.5 part of zinc oxide by weight for each 100 parts by weight of rubber added has given a satisfactory rubber pulp combination. It has been found advisable to run these ma terials through a paint mill with or without a protective colloid, such as glue, sodium oleate and the like, before adding to the beater.

When the beating is finished, agglomeration extending over a considerable period of time and coagulation also extending over quite a longperiod are brought about by a coagulating agent, a zinc su l hate solution being preferred for the s ec 1 c example of the process here describe In order to accomplish these two stages, a 5 to water solution of zinc sulphate is added in quantities sufiicie'nt'not only to completely neutralize the amount of ammonia contained in the stuff in the beater but also to provide an exthird of the coagulant solution is started,

beating of the mass is continued for approximately one-half hour so as to insure thorough mixing of the contents of the beater. The last third of the solution is then added very slowly and with great care. This third is preferably diluted with .water so that the coagulant content is approx mately 1%. This 1% solution is added also through the screen, addition being completed in 30 minutes.

The addition ofthe coagulant causes first an agglomeration and then coagulation. By the term agglomeration is meant that sufficient of the coagulating reagent is added to the material in the beater to cause the Brownian motion of the rubber particles to be substantially diminished and perhaps stopped entirely. If this operation were followed under the microscope it would be seen that the particles at this stage form a chain or clots but that the particles do not coalesce or form a continuous mass of rubber. If the operation were carried out in an ordinary solution of latex in water, the coagulating agent and the solution allowed to stand, ,itwo'uld be found that the rubber particles would gradually rise to the top and form a layer of comparatively high rubber content while the lower layer would be practically clear. If this lower layer were removed and water added so as to make up the original volume, with slight agitation, the particles would again disperse, and the Brownian motion would become re-established in substantially its original amplitude and a true emulsion would result. If an excess of zinc sulphate or other coagulant were added to the material in the beater or the clear latex,as indicated above, it would be found that the individual particles of rubber had coalesced to form acontinuous mass which, after separation and washing with fresh water, could not again be reformed into an emulsion or suspension. By carrying out this process in the beater the agglomerated particles of rubber are completely distributed throu bout the mass of cellulose fiber, and the ad ition of more coagulent fixes them uniformly on the fiber and effects coagulation. It has been found that if the above process is reversed; namely, by adding the latex, after the coagulant has been added, to the stuff in the beater, coagulation in com aratively large lumps takes place thereby ecreasing the uniformity with which the rubber is distributed throughout the mass of fiber. It is also believed, but not definitely pro ven, that there is an actual absorption of the rubber by the cellulose fiber while in the intermediate or agglomeration stage before true coagulation has taken place.

The latex pulp combination so prepared is then'ready to be run on to'the paper machine, such as a Fourdrinier or cylinder machine. The mass is then preferably run through the usual processes for the production of paper, passing to the stufichest then to the paper machine, then on to the dryingcans and then to the calenders, if desired. These processes, on the paper machine, may

be identical with those now practiced in the production of ordinary papers. If the vulcanizing ingredients'before referred'to have been added to the pulp in order to produce a vulcanized paper, the paper-rubber combinations would ordinarily be taken from the drying drums and placed in a chamber heated to F. for four hours, at the end of which time the rubber would be vulcanized and the material can be removed and utilized for any desirable pur ose. If

no vulcanizing agent has been a ded, the

last step in the process just referred to of placing in a heated chamber will not be necessary. However, whether or not vulcanizing ingredients have been added there may be utilized a final step ofsubjectin the sheet to heat and pressure in any suita lo a paratus to obtain a more condensed pro uct.

Various types of materials may be used to provide paper pulp for use in the processes recited. For example, we may use sulpliite, soda, straw or rag or similar stock. In addition or substitution of such materials, asbestos may be employed. In carrying out the invention employing asbestos fibre, such fibre is thoroughly dispersed in water in an ordinary beater such as is used for the preparation of paper pulp. 300 lbs. of asbestos fibre and 6 lbs. of anhydrous ammonia in 29% solution areadded to approximately 5000 lbs. of water in the beater. The material is beaten for about 15 min. in order to give a thorough distribution of the fibers throughout the beater. Since there is no hydration of asbestos fiber it is not necessary to continue longer than the above period. After 15 min. 150 lbs. of

rubber as latex is added after diluting with water to approximately three times its original volume. The latex is added in the same manner as heretofore described in connection with paper pulp. After all the latex has been added the beater roll is raised since it is not desirable to break up the fibers of asbestos. The material is then mixed for one hour. .It is noticed early in this mixing that the milky color caused by the latex gradually disappears. At the end of the above time the liquid in the beater is almost colorless. Zinc sulphate in solu- --:tion is then added to neutralize completely i5? the ammonia contained in the stock in the beater, and to provide a 510% excess over the quantity required for neutralization therein." Upon the addition of zinc sulphate the milky color of the liquid comletely disappears after about half enoug sulphate has been added to completely neutralize the ammonia in the beater. There is no coagulation whatever throughout the mass except that which occurs on the surface of the fibers.

The resulting mass may be satisfactorily run on to the paper machine and handled in every way similar to the manner in which the combination of paper pulp and latex is handled. In place of zinc sulphate papermakers alum may be used if desired.

Although aritgnonia-preserved latex has been indicated in the above process, it will be understood that any suitably preserved latex may be employed. Instead of zinc sulphate itis feasible to use various coagulants, acetic acid, the sulphates, chlorides, nitrates, and acetates of aluminum zinc and iron, or in fact any other coagulant appropriate to the vulcanizing ingredient used when a vulcanized product is desired. linstead of the vulcanizing ingredients herein designated, various other vulcanizing substances, preferably those which operate at low temperature, may be employed.

Various materials may be added along with those mentioned for carrying out the process, such as glue, glycerol, sodium oleate, sodium' stearate, sulphonated oil, etc. The

tendency is, in adding these materials, to

cause the rubber around the fibres of wood, cotton, asbestos. or other material employed to retain a higher-percentage of water and thus to give a more continuous action of the coagulanton the rubber, causing easier working on the paper machine and consequent formation 'of a stronger sheet.

Artificial latices, that is, aqueous dispersions of rubber prepared artificially by dispersing water in rubber in the presence of a hydrophylic protective colloid may be advantageously employed in lieu of natural latex. Undue absorption of moisture by the finished paper may be controlled by dispersing' oils, fats, waxes, resins, etc., along with 1 have -of the cylinder or Fourdrinier machines or other parts of the apparatus and interfere with the Working of these parts. The re- .tention of rubber based on the quantity of rubber solids in the latex employed is approximately 100%.

By the process it is possible to incorporate with the various types of fibre from 1% or less of rubber up to more than 150% based on the weight of the pulp taken.

The characteristics of the paper resulting from the above process-are widely variable depending upon the amount of rubber used,

the kind of pulp used and whether or not the rubber is vulcanized in the sheet, Using concentrations of rubber on the sheet as low as 2% on the Weight of the pulp, increases in Mullen test of from 15 to 20%, tensile strength of from 8 to 10% and resistance to flexing of from 40 to 60% have-been obtained. These properties in general increase as the percentage of rubber in the sheets is made larger. Papers containing rubber are water-resistant even with the lower percentages. After the amount of rubber has been raised to from 10 to 15%, this quality is greatly increased. Papers containing 33 rubber are capable ofbeing washed in water a great number of times without destroying the sheet or materially decreasing its strength. Paper containing above 25% rubber on the weight of the sheet decidedly characteristic properties tending more toward those of a sheet of rubber than of paper in the ordinary sense the claims reference is made to rubber and paper and. similar combinations it will be understood it is intended to cover and include any kind of pulp or short fiber material and particularly asbestos. It will also be understood that the terms rubber latex and latex comprehend the naturally occurring, as 'well as the artificially prepared, aqueous dispersions of rubber. X

As many "a parently 'widely different em-' bodiments ofthis invention may bemade without de arting from the spirit thereof, 1t will be un erstood that we do not intend to limit ourselves tothe specific embodiment herein set forth except as indicated in the ap n'ded claims.

aving thus described our invent1on,\what i we claim and desire to protect by Letters Patent is: I

1. In a process for the manufacture of rubber and paper and similar combinations the steps of combining with pulp a quantity of rubber latex, agglomeratmg the 'rubber subjecting the mass to further mixing, an then coagulating the rubber.

.2. A process for the manufacture of rubber and paper and similar combinations which comprises combining .with alkallne pulp a quantity of alkaline-preserved latex, agglomerating the mass, sub ecting the mass to further mixing, then. coa latmg the mass, and subsequently subjectmg the mass to a method of manufacture whereby it is formed into sheets.

'- 3. A process for the manufacture of rub- .ber and paper and similar combinations -which comprises combining with ammoniatreated pulp a quantity of ammonia-preserved latex," agglomerating the mass, subjecting the mass to further mixing, then coagulating the mass, and subsequently subjecting the mass to a method of manufacturewhereby it is formed into sheets.

4. A process for'the manufacture of rubher and paperand similar combinations which comprises" combining with pulp a quantity of rubber latex and adding a zinc' sulphate solution thereto of such concentration and at such rate that local coagulation is substantially avoided-and that a slow ag- 'QlOlllGI'fitlOIl followed by coagulation "of the mass occurs, and subsequently subjectin the mass to a method of manufacture where y it is formed intosbeets.

5. A rocess for the manufacture of rubberand paper and similar combinations which comprises combining with alkaline pulp a quantity of rubber latex, mixing with the mass :1 coagulanthaving anacid' reaction in insufiicient quantity tmcause it to become acid, subjecting the-mass to .further mixing, then mixing with the mass a further quantity'of the coagulant to cause coagulation, and subsequently subjecting the mass -lo a method of manufacture whereby it is formed into sheets.

6. A rocess for the manufactureof rubber an paper and similar combinations which com rises combinin with ammoniatreated u p a quantity 0 alkali-preserved latex, a ding a coagulant having an acid reaction to the mass in insufficient quantity to cause it to become acid, thereby agglom-' er'ating the mass, subjecting the'mass to further mixing, then continuing the addition of the coagulant to cause coagulation, and subsequent y subjecting the mass to a method of manufacture whereby it is formed into sheets.

7 A recess for the manufacture of rubher an paper and similar combinations which comprises combining with ammonialreated ulp a quantity of alkali-preserved latex, a ding a coagulant having an acid reaction to the mass in insuflicient uantity to cause the mass to become acidt ereby agglomerating the mass, subjecting the mass to further mixing, then adding a further.

'latex to the alkali treated pulp, continuing the beating. until substantially all of the pulp is alkaline, adding a eoa lating. agent having an acid reaction in ilute solution, such agent being added in two stages, ap-' proximately two-thirds of the amount necessary to coagulate the latex being first added, then thoroughly mixing the mass,

then adding the remaining third'of the coagulating agent to cause coagulation of the imass, and subsequently subjecting the mass to a method of manufacture whereby it is formed into sheets. 7

9. A process according to claim 2 in which a low temperature vulcanizing combination is incorporated with the pulp, and vulcanization thereafter carried on.

Signed at New York, county and State of New York, this 19th day of October, 1925.

ERNEST HOPKINSON. LEED P. ROSE/ 

